1. Field of the Invention
The present invention relates to a display device. More particularly, the present invention relates to a display device including a driver IC chip mounted on a substrate.
2. Discussion of the Background
A liquid crystal display (LCD), a plasma display panel (PDP), and an organic light emitting device (OLED) are among widely used flat panel displays.
The liquid crystal display and the organic light emitting device include a display panel provided with a switching element, a gate line, and a data line, and a printed circuit board (PCB) provided with a circuit element such as a signal controller, a driving voltage generator, and a gray voltage generator. The PCB and the display panel may be connected to each other through a flexible printed circuit film.
A gate signal is generated by a driver integrated circuit (IC) chip, which receives signals from the driving voltage generator, and a data signal is generated by the data driver IC chip, which converts gray signals from the signal controller into analog voltages. Each of the gate and data driver IC chips may be a chip on glass (COG) type, a film on glass (FOG) type, or a tape carrier package (TCP) type. With the COG and the FOG types, the driver IC chips are formed on the substrate of the display device, and in the TCP type, a film having the driver IC chips formed thereon is additionally attached to the substrate of the display device. Conventionally, the TCP type has been the most commonly used, but because the size of the IC chips has recently been decreased and for various other reasons, the COG type is now widely used.
When applying the COG type to the display device, a visual inspection (VI) tester to test the operation of the display device is disposed under the driver IC chips. The VI tester includes a testing thin film transistor and constituent elements to connect to a display signal line. Because the size of the driver IC chips is gradually decreasing, the size of the VI tester disposed thereunder may be limited. Particularly, the size of the testing thin film transistor may be limited.
When the size of the testing thin film transistor is reduced, the testing waveform may be distorted by signal delay, productivity may decrease due to the detection of ignorable defects, and spots may be visible due to stress of switching elements inside of the display area.